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Biomedical subjects

F Walker

Publications and source records attributed to F Walker.

At least 55 records · Page 3Linked to original sources
PubMed1996

Proliferation in the normal cervix and in preinvasive cervical lesions.

AIMS: To characterise further the proliferative compartment of the normal cervix and to document its alteration, if any, in the various grades of cervical intraepithelial neoplasia (CIN), particularly changes to the basal epithelial layer; to hypothesise as to the diagnostic and biological significance of any observed differences. METHOD: Proliferative compartments from 86 cervical biopsy specimens (10 normal, 11 with koilocytic change only, 12 CIN I, nine CIN II, and 44 CIN III) were determined using microwave antigen retrieval and a standard three-step Streptavidin biotin peroxidase immunocytochemical technique incorporating the MIB-1 monoclonal antibody (directed against the Ki-67 antigen). Immunoreactivity was assessed as occupying either the lower one third, lower two thirds or all three thirds of the squamous epithelium. Basal cell positivity was also quantitated. RESULTS: Specimens without CIN showed a thin suprabasal proliferative compartment two to four cells thick. True basal positivity was infrequent. With increasing grade of CIN, the growth compartment stretched evermore superficially so that in lesions of CIN III almost the full thickness of epithelium was cycling. In all grades of CIN, basal cell proliferation was significantly increased. CONCLUSIONS: In normal cervix, the parabasal layers represent the main proliferative pool with the basal layer providing a reserve. When CIN supervenes, this proliferative compartment expands commensurate with the grade of dysplasia and as basal turnover is increased specifically the intimate relation between epithelium and basement membrane might be disturbed, facilitating invasion. The diagnostic utility of these changes in growth compartments is limited.

Biopsy↗
PubMed1996

Apnoea and bradycardia during epileptic seizures: relation to sudden death in epilepsy.

OBJECTIVE: To record non-invasively ictal cardiorespiratory variables. METHODS: Techniques employed in polysomnography were used in patients with epilepsy undergoing EEG-video recording at a telemetry unit. RESULTS: Apnoea (> 10, range > 10-63, mean 24 s) was seen in 20 of 47 clinical seizures (three secondary generalised, 16 complex partial, and one tonic) and 10 of 17 patients. Apnoea was central in 10 patients, but obstructive apnoea was also recorded in three of 10. Oxyhaemoglobin saturation (SpO2) dropped to less than 85% in 10 seizures (six patients). An increase in heart rate was common (91% of seizures). Bradycardia/sinus arrest was documented in four patients (mean maximum RR interval 5.36, range 2.8-8.6 s) but always in the context of a change in respiratory pattern. CONCLUSION: Ictal apnoea was often seen. The occurrence of bradycardia in association with apnoea suggests the involvement of cardiorespiratory reflexes. Similar mechanisms may operate in cases of sudden death in epilepsy.

Adolescent↗
PubMed1995

Isolation and partial characterisation of a new strain of Ebola virus.

We have isolated a new strain of Ebola virus from a non-fatal human case infected during the autopsy of a wild chimpanzee in the Côte-d'Ivoire. The wild troop to which this animal belonged has been decimated by outbreaks of haemorrhagic syndromes. This is the first time that a human infection has been connected to naturally-infected monkeys in Africa. Data from the long-term survey of this troop of chimpanzees could answer questions about the natural reservoir of the Ebola virus.

Adult↗
PubMed1995

Reduction in platelet-derived growth factor receptor mRNA in v-src-transformed fibroblasts.

The status of the platelet-derived growth factor (PDGF) receptor in normal rat kidney (NRK) fibroblasts and in NRK fibroblasts transformed by the v-src oncogene or the polyoma middle T (pmt) antigen has been compared. v-src-NRK cells have 7-fold fewer surface binding sites for PDGF than NRK cells, but the affinity of the residual receptors for PDGF is reduced only 2-fold. Levels of the PDGF receptor measured by Western blotting or in an autophosphorylation assay in vitro are 8- and 4-fold lower respectively in v-src-NRK cells than in NRK cells. No PDGF-induced phosphorylation of the PDGF receptor is apparent after 32P-labelling of intact v-src-NRK cells, implying that the reduction in PDGF receptor levels is not a consequence of production of autocrine PDGF. A 10-fold reduction in the amount of mRNA for the PDGF receptor is also observed in v-src-NRK cells. No decrease in PDGF receptor protein or mRNA levels is observed in pmt-NRK cells. We conclude that levels of the PDGF receptor in v-src-transformed NRK fibroblasts are modulated by reduction in the level of PDGF receptor mRNA.

Animals↗
PubMed1995

Interleukin 2 receptor expression and interleukin 2 localisation in human solid tumor cells in situ and in vitro: evidence for a direct role in the regulation of tumour cell proliferation.

Frozen sections of 52 human solid tumours (38 malignant and 14 benign) of varied histogenesis were immunohistochemically stained with well characterised monoclonal antibodies (MAbs) to human interleukin 2 (IL-2) and the alpha and beta chains of its receptor (R). In all malignant specimens, the tumour cells expressed the IL-2R beta subunit (p75) but not the IL-2R alpha subunit (CD25). In 36 of 38 malignant tumours examined, there was conspicuous staining for IL-2 in the tumour cell nuclei/nucleoli and perinuclear cytoplasm. In the human solid tumour cell lines G361 (melanoma), A549 (lung), MCF-7 (breast) and WiDR (colorectal), both subunits of the IL-2R appeared to be expressed, although the alpha subunit only weakly. Exogenous addition of human recombinant (r) interleukin 2 altered cell numbers in 3 of the 4 cell lines (WiDR was refractory). When grown in the absence of exogenously added rIL-2, IL-2 staining was observed in all cell lines. The pattern of distribution was similar to that exhibited by the tumour cells in situ (i.e., a nuclear/nucleolar localisation). In G361 melanoma cells, this IL-2 staining was present in proliferating cells but disappeared as the cultures approached confluence. Addition of an IL-2R beta subunit blocking antibody to growing G361 cultures (grown in the absence of rIL-2) resulted in a significant reduction in cell numbers. We propose, therefore, that the presence of immunoreactive IL-2 and IL-2R expression is characteristic of human malignant cells and that IL-2 may play a role in the autocrine stimulation of proliferation of malignant cells, such as G361 melanoma cells.

Cell Division↗
PubMed1995

A mutation in the epidermal growth factor receptor in waved-2 mice has a profound effect on receptor biochemistry that results in impaired lactation.

The mutant mouse waved-2 (wa-2) is strikingly similar to transforming growth factor alpha-deficient mice generated by gene targeting in embryonic stem cells. We confirm that wa-2 is a point mutation (T-->G resulting in a valine-->glycine substitution at residue 743) in the gene encoding the epidermal growth factor (EGF) receptor. wa-2 fibroblastic cells lack high-affinity binding sites for EGF, and the rate of internalization of EGF is retarded. Although the tyrosine kinase activity of wa-2 EGF receptors is significantly impaired, NIH 3T3 cells lacking endogenous EGF receptors but overexpressing recombinant wa-2 EGF receptor cDNA are mitogenically responsive to EGF. While young and adult wa-2 mice are healthy and fertile, 35% of wa-2 mice born of homozygous wa-2 mothers die of malnutrition because of impaired maternal lactation.

3T3 Cells↗
PubMed1995

Absence of in situ hybridization evidence for latent- or lytic-phase Epstein-Barr virus infection of preinvasive squamous lesions of the cervix.

To investigate whether Epstein-Barr virus (EBV) infection of the uterine cervix plays a significant role in cervical carcinogenesis, 30 preinvasive squamous lesions were subjected to in situ hybridization for (EBER-1,-2, and BHLF1) EBV transcripts which are expressed in latent and lytic infection, respectively. Twenty cases were known to contain EBV sequences by previous polymerase chain reaction (PCR) analysis. Irrespective of EBV PCR status or histological grade, none of the 30 cases demonstrated EBV transcripts in squamous epithelial cells. Two cases showed very occasional EBER-positive stromal cells, most probably representing resident cervical lymphocytes. These findings suggest that EBV plays no part in early cervical carcinogenesis.

Female↗
PubMed1995

Critical influence of timing of administration of granulocyte colony-stimulating factor on antibacterial effect in experimental endocarditis due to Pseudomonas aeruginosa.

The effect of human recombinant granulocyte colony-stimulating factor (hrG-CSF) in rabbits with aortic endocarditis due to Pseudomonas aeruginosa was investigated. hrG-CSF significantly increased the number of polymorphonuclear neutrophils in blood and in cardiac vegetations and the expression of the adhesin molecule CD11b on the surface of polymorphonuclear neutrophils compared with those of animals that had not received hrG-CSF. When treatment was started 72 h after bacterial challenge, hrG-CSF alone had no antibacterial effect and did not enhance the efficacy of ciprofloxacin when used in combination, even with the higher dosing regimen used (50 micrograms/kg of body weight subcutaneously every 12 h for 4 days), in terms of number of positive blood cultures, bacterial counts in vegetations, and survival. In contrast, when treatment was started 30 min prior to bacterial challenge, hrG-CSF (50 micrograms/kg injected every 12 h) decreased bacterial titers in vegetations 72 h later (6.5 +/- 0.9 versus 7.9 +/- 0.9 log10 CFU/g of vegetation for hrG-CSF and controls, respectively; P = prophylactic administration of hrG-CSF did not increase the antibacterial effect of ciprofloxacin. We concluded that the antibacterial effect of hrG-CSF in experimental endocarditis was related to the timing of its administration since hrG-CSF demonstrated a significant but transient antimicrobial effect only when treatment was initiated before bacterial challenge.

Animals↗
PubMed1995

[In situ gene amplification on tissue sections (in situ PCR). A new technique for pathologists].

In situ polymerase chain reaction is a recent technique which combines the sensitivity of PCR reaction to intracellular localization of genomic sequences with the same specificity as in situ hybridization. This reaction is based on the in situ annealing and polymerisation of oligonucleotides complementary to nucleotides located at each side of the target DNA sequence to amplify. We describe the Hot Start PCR (DNA) and the Hot Start PCR after reverse transcription step (RNA). It allows to amplify some nucleic sequences to a high level, becoming easier to detect. The vizualisation can be realized by direct in situ PCR, the product obtained being directly identifiable by incorporation of labeled nucleotides or primers, or preferentially by indirect in situ PCR. In this case, the amplification is followed by in situ hybridization with labeled probes. This last procedure is more specific. Numerous controls are essential at each step of the technique for validating results.

Humans↗
PubMed1994

Management of women with mild and moderate cervical dyskaryosis.

OBJECTIVE: To compare the outcomes in women with mild and moderate dyskaryosis after increasing periods of surveillance and thereby to define a rational protocol for managing such women. DESIGN: Prospective study with randomisation of women to one of four treatment groups, each with a different period of surveillance; one group in which the women were given immediate treatment and three other groups in which the women were under surveillance for six, 12, and 24 months. SETTING: A dedicated colposcopy clinic in Aberdeen, Scotland. SUBJECTS: 902 women who presented with a mildly or moderately dyskaryotic smear for the first time. INTERVENTIONS: Cytological and colposcopic examinations at intervals of six months until the allocated period of surveillance was completed, at which time biopsy was performed. Women with severe dyskaryosis were withdrawn from surveillance and a biopsy was performed. MAIN OUTCOME MEASURES: The histological findings after punch biopsy or large loop excision of the transformation zone, and the trends in cytological appearances of serial cervical smears. RESULTS: 793 women completed the study. In all, 769 women had an adequate final smear, of which 197 were normal cytologically, 328 were still mildly or moderately dyskaryotic, and 244 were severely dyskaryotic. Seventeen of the 67 (25%) women with one repeat smear showing non-dyskaryosis had cervical intraepithelial neoplasia grade III compared with only one of the 31 (3%) women with no dyskaryosis in four repeat cervical smears (P < 0.0001). None of the women had invasive cancer. Of 158 women whose index smear showed mild dyskaryosis and who were allocated to the group under surveillance for two years, only 40 had not defaulted or still had dyskaryotic smears by the end of the two years. CONCLUSION: Cytological surveillance, although safe, is not an efficient strategy for managing women with mildly abnormal smears. Women with any degree of dyskaryosis in a smear should be referred for colposcopy.

Adult↗
PubMed1994

Platelet-derived growth factor stimulates the release of protein kinase A from the cell membrane.

The mitogenic action of growth factors involves the stimulation of intracellular protein kinases. In this report we have characterized the major protein kinase released from Balb/c 3T3 and normal rat kidney plasma membranes by the action of platelet-derived growth factor (PDGF). PDGF appears to stimulate the release of approximately 10 proteins, at least one of which is a kinase capable of phosphorylating proteins on Ser or Thr (as determined by the lability of the phosphate to alkali treatment). More than 90% of the Ser/Thr kinase activity was inhibited by PKI5-22, a specific peptide inhibitor of the cAMP-dependent protein kinase (PKA). We used immunoblotting to confirm that the kinase released in response to PDGF was PKA. cAMP also stimulated the release of PKA, and the set of protein substrates phosphorylated was similar following PDGF or cAMP stimulation. Interestingly, in the presence of a cAMP analogue ((Rp)-cAMPS), cAMP could not induce dissociation of PKA from the membranes, whereas stimulation by PDGF increased the level of PKA activation. Furthermore, unlike Swiss 3T3 cells, neither Balb/c 3T3 fibroblasts nor normal rat kidney cells accumulate cAMP in response to PDGF, yet the level of PKA in the cytosol of these intact cells increases in response to PDGF. Thus, it appears as though PDGF activation of the membrane-associated form of the PKA holoenzyme occurs by a mechanism independent of an elevation in cAMP levels.

3T3 Cells↗
PubMed1994

Dermatomyositis with normal muscle enzyme concentrations. A single-blind study of the diagnostic value of magnetic resonance imaging and ultrasound.

BACKGROUND AND METHODS: It is well documented that the cutaneous lesions of dermatomyositis may precede clinical myositis or may occur in the absence of any muscle disease detectable by current diagnostic criteria. In this single-blind study, we used magnetic resonance imaging (MRI) and ultrasound to evaluate five patients who presented with classical clinicopathologic dermatomyositis, but with normal levels of serum muscle enzymes. This patients group has not been previously studied with these techniques. Patients who served as positive and negative control subjects were also examined. RESULTS: Ultrasonography revealed hyperechogenicity, and MRI revealed high signals on T2-weighted images in several muscle groups of the patient with active myositis (positive control). Increased echogenicity was also noted in the deltoid region of one patient who had previously had a normal muscle biopsy finding. In the same patient, MRI revealed inflammatory changes in the lumbar paraspinal muscles. Another patient, with all previous study results being normal, had MRI evidence of T2 high signals in the gluteus minimus. CONCLUSIONS: Noninvasive examinations such as MRI and ultrasound are beneficial as adjunctive means of examination in the evaluation of patients with dermatomyositis sine myositis or dermatomyositis. Future studies may suggest additional uses for these tests, including serial evaluation of patients, noninvasive confirmation of diagnosis in pediatric patients, or in directing muscle biopsy, thus increasing sensitivity. Ultrasound appears to be the more cost-effective and simple test; but MRI, although more expensive, may be more sensitive and specific.

Adult↗
PubMed1994

Identification of marine organism extracts active at the EGF binding site of human A431 cells.

Using a high throughput radioligand binding assay, we assessed aqueous ethanol extracts from 2885 marine organisms representing 17 phyla from the Indo-Pacific for their capacity to influence [125I]epidermal growth factor binding to human A431 cells in culture. Initial screening employed extracts pooled from five unrelated organisms to cells incubated at 37 degrees C for 20 min. Positive leads from the low stringency screening were pursued using extracts from individual organisms. Extracts from 57 organisms significantly inhibited radioligand binding, five organisms caused the cells to detach from the substrate, while extracts from two organisms brought about an increase in bound radiolabel. To discriminate between the mechanisms of action of the extracts, active organisms were also tested for their capacity to affect radioligand binding in the cells when incubated at 4 degrees C. Those organisms acting only at 37 degrees C were considered to have a cellular site of action, while those also active at the low temperature were considered to exert their effects more directly on the receptor binding event. The acute biochemical activity elicited by the positive organisms was distributed widely between taxa and between geographic regions. The approach provides a sensitive, high volume assay for detecting bioactive substances within marine organisms.

Animals↗
PubMed1994

Flow cytometry CD4+/CD8+ ratio of liver-derived lymphocytes correlates with viral replication in chronic hepatitis B.

T lymphocytes have been assumed to play an essential role in tissue injury in patients with chronic hepatitis B. As hepatitis B virus (HBV) is considered as a major factor controlling liver inflammation, we assessed whether a particular T lymphocyte subset could be preferentially detected in the liver in accordance with viral replication. Liver-derived lymphocytes and peripheral blood lymphocytes were analysed by flow cytometry in 21 patients with histologically confirmed chronic hepatitis B without cirrhosis. Viral replication was quantified by hybridization of serum HBV DNA. Eleven patients exhibited an active viral replication with serum HBV DNA ranging from 10 to 388 pg/ml at the time of the liver biopsy, whereas 10 patients had no detectable serum HBV DNA. In patients exhibiting viral replication, CD4+/CD8+ ratios of liver-derived lymphocytes were significantly higher (P < 0.05) than those obtained in patients without viral replication. In contrast, the percentage of T cells expressing the gamma/delta receptor and that of CD2+/CD57+ cells were similar in both groups of patients. Furthermore, in patients exhibiting viral replication, CD4+CD8+ ratios of liver-derived lymphocytes correlated with serum HBV DNA levels (P < 0.001). No relationship between CD4+/CD8+ ratio of liver-derived and peripheral blood lymphocytes was observed. Our data indicate that, in patients with chronic hepatitis B, the CD4+/CD8+ ratio of liver-derived lymphocytes correlates with viral replication. This suggests that in situ helper/inducer CD4+ T lymphocytes may positively regulate the cytotoxic T cell activity in patients with HBV-related chronic hepatitis.

Adult↗